I recently started working on icons to be added to OOUI, so, to get started, I consulted the Design Style Guide. I was a little surprised to find out that the icons template is done in Sketch a software that is, not only proprietary, but available for macOS only.
I also saw frequent references to "The Noun Project" – apparently a commercial website with freemium model – and to "Material Design" – promoted by Google, whose website relies on analytics from the same company.
A collection of graphics elements and color palettes is hosted in Figma, again a proprietary web-based application.
Similar links are present in other pages of the guide as well.
I found myself wondering if all of this is following principles of the Foundation or even compatibles with them. Shouldn't we rely less on proprietary commercial software and less on closed platform products?